The purpose of this thesis was to clarify the role of external fibrillation in pulp and paper properties. If the degree of external fibrillation could be controlled and the role of external fibrillation were known, this would provide better possibilities for utilizing the full potential of fibrous material.
External fibrillation caused by refining is inevitable, but its role has not been clearly explained, because conventional refiners produce a variety of simultaneous effects, such as internal fibrillation, external fibrillation, straightening or curling of fibers and fines formation. Therefore, a special type of refiner was required for evaluating the specific role of external fibrillation. An ultra-fine friction grinder consisting of two grinding stones was found to overcome the limitation related to conventional refiners.
Using the grinder, it was possible to promote external fibrillation while keeping the internal fibrillation and curl constant. An increase in external fibrils attached to fibers was found to increase the retention of filler during sheet forming in a high-vacuum dewatering device. Promoting the degree of external fibrillation contributed to strengthening the bonding layer between fibers, resulting in improved tensile strength and internal bond strength. Recycling reduced fiber swelling and paper strength, but for externally fibrillated fibers this loss was restored by refining more than for internally fibrillated fibers, even beyond the swelling and strength of the nonrecycled fibers. Increasing external fibrillation alone was found to play an important role in fiber and paper properties, so it can be used as means to control those properties more effectively.

en

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41, [29]

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application/pdf

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en

en

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Helsinki University of Technology

en

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Teknillinen korkeakoulu

fi

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Reports / Helsinki University of Technology, Laboratory of Paper and Printing Technology. Series A